CIIYLIFEROUS SYSTEM. 423 



which collect the lymph from the external parts of the am- 

 phibious animals, and propel it into the veins, appear to 

 be extensively developed in the oviparous vertebrata, no 

 similar moving powers are observed in the course of the 

 chyliferous vessels, which occupy an internal position, the 

 most exposed to the influence of incessant movements from 

 the surrounding parts. The great tenacity of life and 

 irritability observed in these anterior and posterior lym- 

 phatic hearts of the amphibia, which continue to pulsate long 

 after the animals are cut to pieces, is analogous to the per- 

 manence of vitality observed in the chyliferous vessels even 

 in the higher classes of animals, where they continue to ab- 

 sorb chyle from the intestine long after apparent death. 



Most parts of the chyliferous system present a higher 

 grade of development in the reptiles, which is most apparent 

 in the existence of distinct valves in the trunks and larger 

 branches of these vessels, and in the white milky condition 

 of the chyle from the abundance of its globules in the carni- 

 vorous crocodilian family. They are still, however, without 

 mesenteric glands, their valves are less perfect in their struc- 

 ture and function than in birds and quadrupeds, and allow 

 injections to pass easily against their course ; the chyle is 

 still colourless in most of the serpents, lizards, and tortoises, 

 and the ramifications of the lacteals (131. A.), closely accom- 

 pany those of the veins (131. c. m.) and arteries (131./. /.) 

 both on the intestine (131, a. b.), and between the folds of 

 the mesentery. The coarse vegetable food of the chelonia, 

 and the consequent great length of their intestine, give occa- 

 sion for the numerous large chyliferous vessels which cover 

 their alimentary canal and mesentery ; and from the very im- 

 perfect development of their valves, and the consequent faci- 

 lity with which injections pass from trunks to branches, these 

 animals present peculiar advantages for illustrating the struc- 

 ture and functions of this system. Besides forming nume- 

 rous reticulate plexuses by their anastomoses on the intestine, 

 and along the course of the mesentery, the analogues of 

 higher and more complex chyliferous glands, (131. A. e. i.), 

 the trunks of these vessels, by their frequent inosculations, 

 constitute a continuous series of arches along the entire outer 

 margin of the mesentery, much exceeding in number those 

 formed in the same situation by the veins and arteries. The 



